Pneumatic gun mount



March 19, 1957 c. D. BQCK m1. 2,785,606

PNEUMATIC GUN MOUNT 2 Sheets-Sheet 1 Filed April 19, 1954 Fjg. Z.

INVENTORS. I CHARLES D. LBOCK EAR LE P. :5 LANC H D fl ZZZ March 19, 1957 c. D. BOCK ETAL 2,785,606

PNEUMATIC GUN MOUNT Filed April {19, 1954 2 Sheets-Sheet 2 INVENTORS. CHARLES D. BOCK EARL??? BLANCHAED ATTORNEY United States Patent PNEUMATIC GUN MOUNT Charles D. Bock, Floral Park, and Earle P. Blanchard, New York, N. Y., assignors to American Bosch Arma Corporation, a corporation of New York Application April 19, 1954, Serial No. 423,929

9 Claims. (Cl. 89-43) The. present invention relates to machine gun mounts and has particular reference to a pneumatic shock mount.

Recent developments in fire control systems require highly sensitive instruments to be mounted in the gun turret, and in the known gun mounts these sensitive instruments are subjected to periodic vibration forces of undesirably large magnitudes. The present invention converts these periodic transmitted forces to a force of constant magnitude which is an acceptable minimum.

These transmitted forces are reduced by isolating the vibration free surface from the gun through an elastic medium whose resonant frequency is well below that of the lowest expected driving frequency. Sufficient damping is provided in this elastic medium to insure desirable stable performance. The desired stability with relation to the machine gun is the condition where the gun remains between the front and rear mechanical limit stops during the firing cycle. If the gun hits the limit stops, the firing performance may still be considered stable if the transmitted forces are not excessive, although this condition is undesirable. Therefore, the travel of the gun should be limited to only a portion of the distance between the guns limit stops. The'limit stops are separated by a recoil distance which is sufficient to allow the guns motion to be stopped with the same constant force as that required to return the gun to its firing position at the instant of the next succeeding recoil.

In addition to the above requirements, satisfactory operation demands that the peak forces generated by firing the gun be reduced. The elastic medium, therefore, should be capable of absorbing vibratory energy without transmitting a varying force to the vibration free surface. An elastic medium which behaves in this manner is a constant force system wherein the resisting force appears to be independent of displacement.

In the case of bolt reciprocating guns, the system stififness is a factor that influences the inherent rate of fire of the gun and must be set to a certain value to obtain the optimum firing rate.

An additional requirement for the system is that the preload restraining force be altered to compensate for the guns weight vector acting in line with this force when the turret is elevated or when the craft carrying the gun is accelerated.

It will be seen from the discussion above that the shock resisting system should: (a) have a low resonant frequency, (b) have sufiicient damping to insure desirable stable performance, provide proper average recoil in a reasonable space, (d) have a stitfness which produces a satisfactory firing rate, (e) be able to change preload restraining force in accordance with turret elevation or airplane acceleration.

The present invention provides a relatively small, rugged shock resistant mount which possesses all of these properties. In the preferred embodiment of this invention an air cylinder is attached to the turret frame in a position parallel to the gun barrel. The piston in the cylinder is urged against one support of the gun by compressed air in the rear chamber of the cylinder. The air pressure against the piston acts as an elastic medium whose resonant frequency is well below that of the lowest expected driving frequency from the gun recoil and consequently modifies the recoil force transmitted to the turret. The gun support is adapted to slide in the frame and the compressed air absorbs the energy of recoil after each round has been fired and causes the gun to be moved forward before firing the succeeding round. Damping is introduced into the system by means of a constraining orifice in the head of the cylinder through which the air is supplied. This orifice is required to prevent positional travel or walking of the gun from one limit stop to the other during a burst of several rounds, i. e. it offers positional stability.

Suitable spring cushions are employed at the front and rear limits of gun travel to hold the forces transmitted through the stop to a minimum. In one embodiment these spring cushions are modified Edgewater ring spring adapters.

The stiffness of the system is regulated by building the reservoir of the compressed air of the system to a specified volume.

Provision is made for automatically adjusting the cylinder pressure upon deviation of the firing position from the horizontal to maintain the limits of gun travel substantially constant.

The pneumatic soft mount reduces the peak pressures on the sensitive apparatus to a relatively small value which is nearly constant in nature and simulates the action of a constant force spring.

For a better understanding of the invention, reference may be had to the accompanying diagram Fig. 1 which shows schematically the mechanical connections between the elements.

Fig. l is a sectional view of the gun supporting apparatus;

Fig. 2 is a sectional view of the regulating apparatus; and

Fig. 3 is similar to Fig. 2, but shows a modified form of regulating apparatus.

With reference now to Fig. 1, the machine gun 10 is supported on the turret frame 11 by the supports 12 and 13 which are adapted to slide longitudinally with respect to the gun 10 in the frame 11 through a limited distance.

The piston rod 14 of piston 15 rests against the rear edge of the forward support 12, but is not rigidly attached thereto. The piston 15 slides within cylinder 16 in which air pressure is maintained in the chamber between the piston 15 and the end plug 17.

Air is introduced into the chamber of cylinder 16 by means of an air passage 15 in the plug 17, which is connected to the air reservoir 20 by the piping 19. A plate 21, secured to the inner face of plug 17, has a small hole 22 located opposite air passage 18 and acts as a restricting orifice to provide the required damping for the system.

The system thus far described will operate to maintain the machine gun within the mechanical limit stops 32a, 12b and 13a, when the gun 10 is firing at a constant elevation angle, for example, horizontally. Prior to firing operations the gun is urged forward by the air in the cylinder 16 until supports 12 and 13 contact the limit stops 12a and 13a respectively. When the trigger at the control handle (not shown) is depressed, the first round is fired and the recoil therefrom drives the gun 1% toward the rear, compressing the air in cylinder 16.

At some time during the rearward travel, the compressed air stops the motion of the gun, and then begins to urge the gun It forward. During this forward motion the next round is fired by the gun mechanism, not described here. This action is repeated as long as the trigger is depressed.

Since the system of Fig. 1 is designed primarily for steady state conditions, the recoil of the first round may not be completely absorbed in compressing the air, and the supports l2 and 13 may hit the limit stops 12b and 13b respectively. During subsequent rounds however, the recoil will be acting against the forward momentum of the gun and the air in cylinder 16, and the gun will remain out of contact with the limit stops.

The travel of the gun depends upon the pressure in reservoir 29. With low pressure the gun begins its forward motion later and may even reach the rear limit stops 12b, 1311 after each round. With high pressure, the gun begins its forward motion earlier and may even reach the forward limit stops 12a, 13a. The pressure in reservoir 2t), the position of the end plug 17 and the size of orifice 21 are all selected so as to keep the travel of the gun approximately centered during the steady state condition.

Whenever the turret 11 is depressed or elevated, or when the turret is undergoing acceleration, the optimum pressure in reservoir 2% must be changed to account for the additional force rearward or forward provided by the weight of the gun. To this end the pressure in reservoir 26 is automatically regulated by the apparatus shown in Fig. 2.

The air to reservoir is supplied by appropriate piping through regulator 23 and three-way valve 24 from the air supply 25, which may be a tank of high pressure air, or a pump maintained supply. The regulator 23 has a pressure sensitive diaphragm 26 to which one arm 2'7 of a pendulum rod 28 is attached. A second arm 29 of the rod 23 actuates the three-way valve 24, and a third arm 39 of the rod 28 is connected to a mechanical damping device 33. A weight 32 is carried by rod 23, the upper end of which is pivoted on turret frame 11.

When the gun is horizontal the regulator 23 is located in a position such that the desired pressure within reservoir 2t) and regulator 23 maintain the diaphragm 26 in such a position that rod 28 hangs vertically.

If the gun is depressed, the weight 32 will cause the pendulum rod 2% to turn about its pivot (clockwise in Fig. 2), thereby distending the diaphragm 26 and actuating the valve 24 to the left to connect the regulator 23 to the atmosphere. In this manner, the pressure in reguiator 23 is decreased until the diaphragm is returned to the neutral position and valve 24 is closed.

If the gun is elevated, on the other hand, the weight 32 will cause a counterclockwise rotation of pendulum rod 28 such that arm 27 tends to compress the diaphragm 26, and valve 24- is operated to connect the regulator 23 to the high pressure air supply 25. When the air pressure in regulator 23 rises sufliciently, to force the diaphragm 26 to the neutral position, the valve 24 closes.

Although a pendulum actuated compensation means has been described in the foregoing, it is not intended to limit the invention thereto and it will be evident that other systems which are responsive to vehicle accelerations may be employed if desired. By way of example, one alternate arrangement would be produced, as shown in Fig. 3, if the pendulum ro-d 28a is disconnected at the pivot while weight 32a is centered by springs S and adapted to slide horizontally. The compensating unit would be influenced by aircraft acceleration and altitude in exactly the same manner as just described for the pendulum controlled compensator.

Thus, it will be seen that whenever the gun is depressed, the air pressure in reservoir 20 is decreased accordingly, and whenever the gun is elevated, the air pressure in reservoir 20 is increased accordingly to maintain the limits of gun travel substantially constant. The weight 32 and regulator 23 must be chosen to give the desired results. The mechanical damping means 31 reduces the sensitivity of rod 28 of vibratory forces, so that rod 28 is displaced only upon tilts of frame 11 from the horizontal or upon sustained accelerations of the craft.

In a similar fashion, the effects of craft acceleration are accounted for, since the pendulum rod 28 is deflected to the right in Fig. 1 during forward acceleration thereby increasing the pressure in tank 20, and is deflected to the left during deceleration thereby decreasing the pressure in tank 20.

We claim:

1. In a device of the character described, a frame, supporting means mounted for reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source of pneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system.

2. In a device of the character described, a frame, supporting means mounted for reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source of pneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system and a pendulum for controlling the pneumatic pressure in said source of pneumatic pressure.

3. In a device of the character described, a frame, supporting means mounted for reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source of pneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system and a pendulum for controlling the pneumatic pressure in said source of pneumatic pressure, said pendulum comprising a Weight responsive to frame accelerations and valve means operatively connected to said pendulum.

4. In a device of the character described, a frame, supporting means mounted for reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source of pneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system and a pendulum for controlling the pneumatic pressure in said source of pneumatic pressure, said pendulum comprising a weight responsive to frame accelerations and valve means operatively connected to said pendulum and a regulator operatively connected to said pendulum for counteracting the effect of the accelerating forces on said pendulum.

5. In a device of the character described, a frame, supporting means mountedfor reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source ofpneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a

piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system and a pendulum for controlling the pneumatic pressure in said source of pneumatic pressure, said pendulum comprising a weight responsive to frame accelerations and valve means operat-ively connected to said pendulum and a regulator operatively connected to said pendulum for counteracting the effect of the accelerating forces on said pendulum, said regulator comprisin a chamber communicating with said source of pneumatic pressure and a diaphragm in said chamber operatively connected to said pendulum.

6. In a device of the character described, a frame, supporting means mounted for reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source of pneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system and compensation means for controlling the pneumatic pressure in said source of pneumatic pressure.

7. In a device of the character described, a frame, supporting means mounted for reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source of pneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system and compensation means for controlling the pneumatic pressure in said source of pneumatic pressure, said compensation means comprising a weight responsive to frame accelerations.

8. In a device of the character described, a frame, supporting means mounted for reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source of pneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system and compensation means for controlling the pneumatic pressure in said source of pneumatic pressure, said compensation means comprising a weight responsive to frame accelerations and V a regulator operatively connected to said pendulum-for counteracting the effect of the accelerating forces on said pendulum.

9. a In a device of the character described, a frame, supporting means mounted for reciprocal movement on said frame, said supporting means being adapted to support a gun in operative position, means for checking the recoil of the gun and returning it to firing position, said means comprising a source of pneumatic pressure, a cylinder communicating with said source of pneumatic pressure, a piston in said cylinder, a piston rod operatively connected to said piston and engaging said supporting means and a restriction in the air path between said source of pneumatic pressure and said cylinder, said restriction providing damping means for the system and compensation means for controlling the pneumatic pressure in said source of pneumatic pressure, said compensation means comprising a Weight responsive to frame accelerations and V a regulator operatively connected to said pendulum for References Cited in the file of this patent UNITED STATES PATENTS 550,654 Spiller Dec. 3, 1895 1,519,215 Moriarty Dec. 16, 1924 1,582,759 Joyce 'Apr. 27, 1926 Prache Nov. 6, 1951 

